Many currently available color ink-jet printers employ a cartridge having an ink reservoir divided into three distinct chambers, each chamber holding ink of one of three primary colors. Architecturally, such color cartridges are more complicated than monochrome cartridges because the ink flow pathways from the three chambers must converge into a very small region at the print element. The fabrication process often dictates constraints on the basic functional requirements of the pathways. Such constraints can lead to a pathway design wherein it is difficult to prime the pathways during initial ink fill, or a design which will not function reliably when air bubbles are ingested during normal handling and operation.
It is known that air bubbles, because they assume a nearly spherical shape, can be prevented from completely blocking an ink flow pathway by providing the pathway walls with irregularities. EP application no. 92-3707379.5, suggests ink flow pathways having grooves in the walls. However, the provision of grooves in the pathways causes problems in the making of the cartridge body. The grooves and ink flow pathways are formed in the cartridge body as the cartridge body is molded. To form the grooves, the mold tool must have a mold core pin with ridges conforming to the widths of the grooves. The grooves are very narrow hence the width of the ridges on the core pin must be quite small and may be easily damaged. Furthermore, molds are frequently polished during final conditioning and ridges on the core pin interfere with polishing the core pin.
A further disadvantage of grooves is that they must extend to an outer surface of the cartridge body so that the core pin carrying the ridges which form the grooves, may be withdrawn from the pathway.